Ethanol, or alcohol as it is commonly known, is an organic chemical which is extremely soluble in water. This is unlike most organic chemicals and is due to the hydroxyl group in the structure. Ethanol also has the odd characteristic that it forms an azeotrope with water at 96%. An azeotrope is a mixture of two chemicals which form a constant boiling point mixture. This means that 96% ethanol cannot be separated into its components by simple distillation.
However, by a process known as azeotropic distillation, an ethanol content exceeding 99,9% can be achieved. In this process a third component is added to the mixture and this component is selected because of its greater affinity for one of the components in the mixture. Distillation will now separate the two from the third component (ethanol) which can then be recovered. A more recent technology, molecular sieving, will also separate the water from the ethanol.